Semaphore-arm.



W. A. DUNLAP.

, SEMAPHOHE ARM.

APPLICATION FILED AUG-5. x915.

Patented June 26, 1917.

Flag.

INVENTOR uwlixiuulalili WITNESSES 6144M VV'IIJLLIAM A. DUNLAP, OF PITTSBURGH, PENNSYLVANIA.

SEMAPHORE-ARM Specification of Letters Patent.

Patented June 26, 191 "Z.

Application filed'August 5, 1915. Serial No. 43,789;

To all whom-it may concern:

Be it known that'I, l/VILLIAM A. DUNLAP, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, a citizen of the United States, have invented or discovered certain new and useful Improvements in Semaphore-Arms, of which im provements the following is a specification.

My invention relates to improvements in the construction of semaphore arms such as are used in signaling apparatus on railroads and elsewhere, and its object is to produce an enameled sheet-metal semaphore arm which shall be durable in service.

Certain advantages of a semaphore arm of enameled ware over a painted Wooden arm are readily recognizable; notably the advantagethat the color does not fade. But there are certain disadvantages which have thus far nearly if not entirely outweighed the advantages. One of the conditions of serv ice is that the arm shall swing rapidly om one position toanother and shall stop abruptly when each succeeding position is reached. An arm of sheet metal is relatively heavy, itsinertia relatively great; but the material is in greater or less but in a substantial degree ductile; and the consequence is that sheet metal arms of ordinary construction are liable to bending buckling and breaking near theirpoint of support. This defect has in some degree been overcome by warping the sheet-metal arm, making it curved or slightly V-shaped in cross section, and manifestly an arm so shaped isstronger to resist strains of the nature indicated than an arm formed of sheet metal which extends all in a single plane. But the curved or V- shaped armin turn is not satisfactory. In storms it is liable to become weighted with and its signal-giving surface to become more or less completely covered with snow. The added weight tends to counteract the advantage gained by the special shaping of the arm, while the concealing of the surface tends to render the semaphore invisible. The semaphore arm of my invention is strengthened to resist strains which tend to bend, buckle, and break it, andis more effectively strengthened to this end than any other sheet-metal semaphore arm heretofore made, and at the same time it does not have exposed to storm any reentrant angles or concavities, in which snow may lodge and collect, with such untoward consequences as are indicated above;

Another difliculty which has heretofore obtained in the use of enameled ware semaphore arms has been that, when securely fastened totheir supporting member, the strains of securing them and the strains of service have caused the enamel coat to crack and break away, particularly from those portions of the surface immediately adjacent the securing and supporting means. If they be bolted, as ordinarily they are, to a quadrant-shaped iron plate, the enamel will in the course of service break away from the metal near the place of bolting. This diffieulty too I overcome. Other advantages will appear in the course of the ensuing description.

Referring to the drawings, Figure 1- shows in side elevationa semaphore arm of my invention; Fig. 2' shows it in plan; Fig. 3 is a- View in vertical longitudinal section and on larger scale of the inner end of the arm-the end which is secured to the supporting member; Fig. 4 is a view in transverse section through the arm, the plane of section being indicated bythe dotted line IV-IV, Fig. 3; Fig. 5 is a transverse section on the plane indicated by the line V-V, Fig. 3; Fig. 6 is a view in medial horizontal longitudinal section of the inner end of the arm, the planes of the two sections of Figs. 3 and 6 being at right angles one to another; Fig. 7 is a vertical longitudinal section of an arm differing in detail from the arm of Figs. 1-6.

The feature of my invention which I shall first describe will be understood on comparing Figs. 1 and a The semaphore arm is composed of two sheets of metal 1 and 2 arranged face to face, secured to one another along their edges but separated one from the other at a varying interval throughout the intermediate portions of the sheets. The two sheets are in this instance bowed out wardly one from another in simple curves, and the two bowed sheets are brought together and secured together with their concave faces inward. Thus it will be observed that the arm as a whole is in structure a girder, and possesses this characteristic feature of a girderz that the strains of the na ture indicated and which have been found to be so destructive of sheet-metal semaphore arms made of a single sheet of metal, and which tend to cause bending, buckling, and breakingstrains which increase in intensity from the outer end of the blade inward and are of greater intensity immediately adj acent the point of support-these strains are resisted and distributed in the girder. The part of the girder better disposed to resist strain serving to relieve the part which otherwise would be subject to undue strain.

This semaphore arm of my invention, formed of two sheets of metal and possessing by virtue of the non-parallelism of the plates transversely of the arm the characteristic feature of a girder, is preferably of the specific lenticular shape illustrated in Fig. A. It will be understood, however, that the characteristic features of a girder may still be retained though that specific shape be departed from; and, accordingly, it will be found in the ensuing claims that the invention is not in its broader definition limited to this specific shape. But this specific shape is further advantageous. Being doubly convex it sheds snow and sleet as an arm with a reentrant curve or angle will not; and being curved in a simple convex curve, a maximum of strength is combined with a minimum of liability to the collection of snow and ice.

At the outer end of the arm the lenticular cross section is interrupted by the plane surfaces, a, b, 0, whose arrangement and disposition will be fully understood on comparing Figs. 1 and 2. At this end the strains dwelt on above are at a minimum and are quite negligible. By providing the surfaces a, b, 0, the outer end of the arm is tapered off to the edge a I), along which edge as along the lateral edges of the arm the two component plates are united. The fish-tail end of the arm shown in Fig. 7 merely requires an obvious modification of the planes which form the taper. This plane a b 0 of Fig. 1, or these planes a 0 cl, 1) 0 (Z of Fig. 7, are further advantageous in service. It will be observed of them that, regarding the arm as a whole, and viewing it longitudinally from end, they interrupt the continuity of the signal-giving surface and are angularly disposed with respect to the main portion of the signal-giving surface. These angularly disposed surfaces at the outer end of the arm have practical value, because under certain conditions (when installed on curves for example) they will be visible and give the desired signal to an approaching train while still at a distance so great or in a relative position such that the main signalgiving surface may not be clearly discerned. The semaphore arm with the interrupted signal-giving surface which I have now described may at times and under changing conditions of light be read at greater distance and under more difficult conditions for seeing than an arm with uninterrupted surface.

At its inner end, the end by which it is supported, provision is made for the bolting of the semaphore arm to the member which carries it, in such manner that the breaking away and arring loose of the enamel coating of the arm is prevented or at least the liability to such injury is greatly diminished. The body metal available and practicable for such enameled ware is of course sheet steel, and steel is a material which is relatively hard and unyielding. My improved semaphore arm is as has already been explained hollow, and I introduce at the inner end of the arm a filling 3 of rigid but relatively elastic material, such as wood, so that the arm as a whole (at least throughout that portion of its length through which the supporting bolts pass) is not a hard and unyielding and shock transmitting body of steel alone, but, being composed of wood and steel combined, is relatively soft and yielding and shock absorbing. And, further, and to the same end, I line the bolt holes formed through the arm for the passage of the supporting bolts with bushings A of such soft material as brass, and I cause these bushings to extend beyond the holes on either side of the arm and to overlie opposite faces of the arm and form a packing 5 between the opposite faces of the arms and the heads and the nuts of the securing bolts. Thus the sheets of enameled metal,

while securely held, are held between memhere which yield and shape themselves when being applied, and members which are relatively shock-absorbent when the whole structure is assembled. And by these means the enameled surfaces of the arm are protected against injury, otherwise incident to assembling and use.

A semaphore arm of ordinary construction is of increasing width from its inner to its outer end. The extreme inner end may be made of uniform width for a suflicient distance to provide for attachment. This is indicated in Figs. 1 and 3. The filler 3 then may be introduced from the inner end of the arm as a single block. If, however, the arm is tapered all the way to its extreme 1nner end, as is the case in the arm shown in Fig. 7 the filler 3 may, as indicated in that figure, be made in a plurality of parts, applicable still from the inner end. The otherwise open inner end of the arm may, after the introduction of the body of filler, be closed by a cap 6.

It is convenient, though by no means requisite, to modify the cross-sectional shape of the arm at its inner end, changing the girder shape of Fig. 4 to the rectangular shape of Fig. 5. This modification in shape makes for cheapness of manufacture and facility and security in application; and, since the inner end of the arm is securely bolted to its support, the strains tending to injury and destruction are not exerted upon it. These strains however are greatest immediately adjacent the supporting bolts. Comparison of Figs. 1, 2, 3, and 6 will show the filler block 3 extending outward beyond the portion of the arm which is rectangular in cross section and into the portion which is girder-like in cross section. Thus the filler block reinforces and strengthens the arm against bending, buckling and breaking to the point where by virtue of its girder-like shape it is strong to resist such injury. Manifestly the filler block may be prolonged outward from the bolt holes so far as may be found expedient or desirable.

It will be observed of the semaphore arm Which I have described that it is complete in itself and requires no supplemental blocks, pads, or other devices by which to accomplish its proper attachment to the parts by which it is supported.

I claim as my invention:

1. A semaphore arm whose opaque, lightreflecting, signal-giving surface is in its longitudinal extent interrupted and disposed at different angles to the sight of the observer.

2. A semaphore arm of lenticular cross section throughout its medial portion and provided at its outer end with opposite oblique plane surfaces.

3. A semaphore arm composed of enameled metal plates inclosing a filler of elastic material and provided with bolt holes extending through both plates and filler.

4. A semaphore arm composed of enameled metal plates inclosing a filler of elastic material and provided with bolt holes extending through both plates and filler and bushings of packing material extending through said bolt holes and overlapping the outer surfaces of said plates.

5. A semaphore arm composed of a plu rality of plates shaped to girder form, such girder form being modified at the inner end of the arm and the said plates there extending in )arallelism, and a filler block introduced between said plates and extending from the portion of the arm in which the plates are parallel and into the portion in which the plates are shaped to girder form.

6. A semaphore arm composed of a plurality of plates, lenticular in cross section throughout its medial portion and rectangular in cross section at its inner end, and a filler arranged between the plates at the 1nner end of the arm and extending into the lenticular shaped medial portion of said arm.

In testimony whereof I have hereunto set my hand.

WILLIAM A. DUNLAP.

lVitness FRANCIS J. TOMASSON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, 11. e." 

